Pulverized coal atomizer



March 20, 1951 E. E. HEWITT 2,545,513

PULVERIZED COAL ATOMIZER Filed April 29, 1948 INVENTOR. Ellis EHBLUILUBY AT T ORNE'Y Patented Mar. 20, 1951 PULVERIZED COAL ATOMIZER Ellis E.Hewitt, Edgewood, -Pa., assignor to The Westinghouse Air Brake Company,Wilmerding, Pa., a corporation of Pennsylvania Application April 29,1948, Serial No. 24,073

This invention relates to variable area orifice devices and moreparticularly to a device for atomizing pulverized coal or the like.

2 Claims. (Cl. 24139) The variable area orifice device, as a pulverizedcoal atomizer, may be employed in a coal burning gas turbine plant ofthe type described in the copending U. S. application of Harry C. May

and Ellis E Hewitt, Serial No. 22,208, filed April 20, 1948, andassigned to the assignee of the present application. The device maycomprise a casing having an inlet opening adapted to be supplied with amixture of pulverized coal and conveying air, an outlet opening adaptedto be connected to a combustion chamber for sup plying a mixture ofatomized coal and conveying air thereto, and a fluid pressurecommunication extending between the above named openings for conveyingcoal and air therethrough. Fixed and adjustable orifice elements mayproject into the fluid pressure communication in the path of flow of thecoal and air mixture to define a restricted flow area through which saidmixture must flow. The coal and air mixture entering the inlet openingat a relatively high pressure suddenly expands in passing through therestricted fiow area defined by the fixed and adjustable orificeelements to the outlet opening. Due to this sudden expansion of the coaland air mixture, the compressed air that has permeated into the pores ofthe coal entering the device cannot escape rapidly enough to attain thepressure in the outlet opening, so that the coal is exploded intoextremely small powder-like par? ticles. The flow area is made variableby adjustment of the adjustable orifice element to assure that a desiredpressure drop through the device may be attained for various pressureconditions in the inlet opening.

The adjustable orifice element may be in the form of a cylindricalshaped member slidable in a hole or sleeve in a direction transverselyofthe fluid pressure communication and having a tapered wedge-shaped endportion projecting into said communication for regulating flowtherethrough. A rod or actuating stem is attached to the adjustableorifice element through the medium of which position of the taperedportion of said orifice element may be adjusted in the communication.The stem must extend through an opening in the casing to allow foradjustment from without, the outer end off said stem being adapted forconnection with a positioning device or the like. Due to the slidablerelationship between the adjustable orifice element andthe stem with itsguiding surface, suf-' ficient clearance must be provided to allow for acertain degree of freedom of movement in order that said orifice elementmay be positioned easily and accurately. Such clearance, even thoughonly in the order of several thousandths of an inch, inherently affordsa path through which extremely fine powder-like particles of pulverizedor atomized coal from the fluid pressure communication might escape fromthe device to the atmosphere and, due to the potential explosive natureof a mixture of powdered coal and air, present a hazard to the safety ofmen and equipment.

It is therefore one object of this invention to provide a variable areaorifice device of the above type for use in atomizing pulverized coalwhich will not allow unintentional escape of atomized coal therefrom.

At the same time, clearance around the cylindrical portion'of theadjustable orifice element opento the fiuid pressure communication alsoaffords a space in which the extremely fine particles of pulverized oratomized coal may accu-' mulate and pack to cause an undesirableresistance to positioning adjustment of said element as well as causingundue wear to related parts due to abrasive properties of said coal, andit is I therefore another object of the invention to provide means whichwill assure" that such clearance will remain free of coal.

Other objects and advantages will become apparent from the followingdetailed description of the invention.

In the accompanying drawing, the single figure is a diagrammatic view,partly in outline but substantially in section, of a variable areaorifice device particularly adapted for use as a pulverized coalatomizer and embodying the invention.

Description As shown in the drawing, the pulverized coal atomizer maycomprise a casing I havin an inlet chamber 2 for connection with asourceof pulverized coal and conveying air (not shown), and an outlet chamber3 for connection to a pipe or device to which it is desired to supplyatomized coal, such as a combustion chamber or the like (not shown).Intermediate the chambers 2, 3 are disposed two aligned orifice elements5, 6. Both elements 5, 6 may be substantially cylindrical in shape andprovided with a wedge-shapedend portion 1 for projection into the pathof fio'w of coal and air to define a restricted opening 8 through whichthe mixture of pulverized coal and conveying air supplied to chamber 2must fiow to reach chamber 3. Due to the restriction imposed by elements5, 6 to flow of pulverized coal and conveying air supplied to chamber 2,a sudden drop in pressure is realized as said coal and air flows throughopening 8 into chamber 3. Through the tendency for the air trapped inthe pores of the coal to expand to equalize with the reduced pressure inchamber 3, such coal is exploded or atomized.

Element is fixed, being removably secured to casing I by means of anintegral threaded stem 9 and a nut I0. An annular recess, in casing I isprovided to accommodate element 5 which may be aligned therein by meansof a pin II, and to allow said element to be easily removed from thecasing, a bore I2 is provided through which stem 9 may extend to allownut Hi to be.

disposed outside the casing. An annular sealing element !3 encirclingbore I2 and arranged to be clamped between the element 5 and the casingis provided to prevent escape of atomized coal and air around saidelement and through said bore to the atmosphere.

The orifice element 6 is adjustable to positions toward or away from theelement 5 to adjust the size of the restricted area 8 in order to assurethat drop in pressure experienced by the coal and air in passingtherethrough from chamber 2 into chamber 3 will be adequate to causeexplosion of the pulverized coal particles for various conditions ofpressure in chamber 3. The cylindrical portion of element 6 may beslidably guided in a sleeve member I5 having a press fit in a bore IS ina casing portion I of the casing I. An opening I! in the casing mayallow for projection of element 6. A stem 2!! formed integrally withelement 6 may be provided as a medium through which said element may beadjusted, said stem extending outwardly through a bore 2I in casingportion I. Stem may be of lesser diameter than that of the bore H andmay be slidably guided in a bushing 22, press fit into said bore. An eyebolt 23 or the like is attached to the outer projecting end of stem 20by a screw-threaded connection to provide for connection of said stem toactuating or positioning means (not shown) for adjusting the position ofelement 6 through inward and outward movement of said stem. A pin 24 maybe provided in stem 20, arranged to ride in a groove 25 to guide element6 and to cooperate with a shoulder 25 to definea stop limit for movementof said stem and element in one direction.

The fit between the element 6 and sleeve I5 and between the stem 20 andbushing 22 must be relatively loose to allow said element and stem to bepositioned easily. Thus a clearance space 3% is provided between element6 and sleeve I5. Actually, the clearance space may be in the order ofseveral thousandths of an inch and therefore for sake of illustrationsaid clearance space is greatly exaggerated in the drawing.

According to the invention a fluid pressure chamber is provided incasing portion I at one end of the clearance space 30, the opposite endof which space is open to chambers 2 and 3 in which the mixture of coaland conveying air at relatively high pressures may flow. The fluidpressure chamber 35 is connected to a fluid pressure conduit 36 whichmay in turn be connected to a source of fluid at a greater pressure thanthe pressure of fluid in chamber 2.

The fluid in chamber 35, being of greater pressure than that in chambers2 or 3, will tend to flow through clearance space 30 into said chambersand maintain said clearance space free of the extremely fine particlesof coal traveling through the atomizer. Such flow of air from thechamber 35 through clearance space 30 into chambers 2, 3 will thusprevent leakage of a highly explosive mixture of coal dust and air tochamber 35 and thence to the atmosphere around stem 20 as well aspreventing excessive wear of sleeve I5 and element 6 which otherwisemight occur should fine particles of coal be allowed to accumulate orpack in said clearance space. Since. air supplied to chamber 35 willalso tend to leak around stem 20 through bushing 22 to atmosphere, saidbushing is also kept free of dust and dirt which otherwise might tend toaccumulate and/or pack therein. Therefore, freedom of movement of boththe element 6 and the stem 20' is maintained, so that said element maybe positioned easily at all times.

Summary It will now be seen that I have provided an improved variablearea orifice device particularly adapted for atomizing pulverized-coalor the like which will not allow unintentional escape of even the finestparticles of said coal to the atmosphere. Further, in the improvedvariable area orifice device, the fine particles of coal are preventedfrom entering the clearance spaces between sliding elements, so thatsaid elements are not subjected to the abrasive or restraining action ofsuch coal.

Having now described the invention, what I claim as new and desire tosecure by Letters Patent, is:

1. A pulverized coal atomizer comprising a casing having an inletchamber adapted to be supplied with a mixture of pulverized coal andconveying air under pressure and an outlet chamber adapted to beconnected to receiving means, fixed and adjustable orifice elementsinterposed between said inlet chamber and said outlet chamber to definea restricted opening through which said pulverized coal and conveyingair from said inlet opening must pass to reach said outlet opening, saidfixed orifice element being mounted in a recess in said casing, meansfor locating said fixed element within said recess, a threaded stemattached tov said fixed orifice element extending outwardly through anopening in said casing, a nut attached to said stem, and sealing meanscooperable with said fixed element and with-said casing to preventleakage of coal particles from said inlet and outlet chambers to theatmosphere.

2. A pulverized coal atomizer comprising a casing having a fluidpressure communication adapted to receive pulverized coal and conveyingair under pressure at one end and to deliver atomized coal and conveyingair at its opposite end, fixed and adjustable orifice elementsprojecting transversely into said fluid pressure communication to definea restricted opening through which coal and air traveling through saidcommunication must pass, said adjustable orifice element comprising acylindrical portion slidably mounted within a casing bore with clearanceopening at its one end into said fluid pressure communication, a fluidpressure chamber formed in said casing at the opposite end of saidclearance and adapted to be supplied with air at a pressure greater thansaid conveying air pressure, a stem attached to said adjustable orificeelement extending outwardly through an opening in said casing, a stopelement secured to said stem and projecting transversely therefrom intoa groove in said casing to slidably guide longitudinal move- 5 ment ofsaid stem, and a link element secured to the outer end of said stemadapted for pivotal connection with actuating means for adgjustingposition of said adjustable orifice element through said stem.

ELLIS E. HEWITT.

REFERENCES CITED Number 6 UNITED STATES PATENTS Name Date Joule July 22,1924 Huff July 31,1928 Mason Aug. 15, 1933 Pigott Jan. 1, 1935 Holt Mar.30, 1943

